Normally, to record a file on a storage medium (10A), as shown in FIG. 1, the file system area (11A) includes data size, starting location, and file fragment information, etc. and the actual data is stored in the data area (13A).
If the actual data of the file stored in the storage medium (10A) is divided over clusters 3, 4, 21 and 30 of the data region (13A), the operating system acquires file information from the file system area (11A) to read the file stored on the storage medium, and by reading the clusters in the order 3→4→21→30, can load the file.
If the file saved on the storage medium (10A) is deleted, the actual data stored on the data region (13A) is not erased; instead, the file is treated as deleted by deleting 1 byte of the file data from the file system region (11A).
Therefore, although the file has been deleted, if the file system region (11A) has not been overwritten with different data, and the data area (13A) has not been overwritten with a different data either, recovery of the deleted file by loading the file using the same method for files whose operating system has not been deleted is possible.
However, there was the problem that if the file system area (11A) or data area (13A) where the deleted file was is overwritten with different data, the deleted file could not be recovered.
Also, in the case of video files, they are stored in fragments due to their large size, and in the course of usage of the storage medium (10A) after their deletion, parts of the video data are overwritten in many cases, and there is a high tendency of data loss due to the large space used by the file system region (11A) and data region (13A). Therefore, data could not be recovered when recovering data using file system information.